import math
def hoge(a):
    return a * a
x1, y1, x2, y2 = map(float, input().split())
print (math.sqrt(hoge(math.fabs(x1-x2)) + hoge(math.fabs(y1-y2)))) import math math def hoge(a):
    return a * a hoge return a * a a * a a a a a x1, y1, x2, y2 = map(float, input().split()) x1 map(float, input().split()) map float input().split() ().split () input split y1 x2 y2 print (math.sqrt(hoge(math.fabs(x1-x2)) + hoge(math.fabs(y1-y2)))) print math.sqrt(hoge(math.fabs(x1-x2)) + hoge(math.fabs(y1-y2))) math.sqrt math sqrt hoge(math.fabs(x1-x2)) + hoge(math.fabs(y1-y2)) hoge(math.fabs(x1-x2)) hoge math.fabs(x1-x2) math.fabs math fabs x1-x2 x1 x2 hoge(math.fabs(y1-y2)) hoge math.fabs(y1-y2) math.fabs math fabs y1-y2 y1 y2 x2, y2 = map(float, input().split()) map(float, input().split()) x2 x1, y1, x2, y2 = map(float, input().split()) map(float, input().split()) x1 y2 = map(float, input().split()) map(float, input().split()) y2 def hoge(a):
    return a * a def hoge(a):
    return a * a hoge y1, x2, y2 = map(float, input().split()) map(float, input().split()) y1
import math
def hoge(a):
    return a * a
x1, y1, x2, y2 = map(float, input().split())
print (math.sqrt(hoge(math.fabs(x1-x2)) + hoge(math.fabs(y1-y2))))
